<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    let a = 1
    let sum = 0
    while(a<100){
        a++
        if(a%3==0){
            sum=sum+a
        }
        // j+=3(也行)
    }
    console.log(sum)

</script>
</html>